# Homework Help: Compton Scattering Experiment

1. Oct 17, 2004

### Bobster

Any ideas how to do this question ?

In a Compton type experiment X-rays scattered through 90 degrees suffered one percent reduction in energy.What was the incident energy of the X-rays ? You can assume that the electron coiled non-relativistically.

Any help would be really appreciated !

Bob

2. Oct 17, 2004

### Bobster

Oh by the way,i used the equation :

dL=h/mc (1-cos angle)

and i got dL=2.43 E -12

Since the energy reduction is 1 % i did

hc/L-hc/L' =0.01

and L'=L+2.43 E -12

so we end up with a quadratic :

L^2 - (2.43 E -12)L-(4.83 E -35)=0

Solving I got, L= O or -2.43 E -12

Hence incident energy is hc/0 or hc/-2.43 E -12

=> energy =infinity :surprised or hc/(-2.43 E -12).

Now is this total rubbish,or am I getting somewhere ?

Cheers for any help !
Bob

3. Oct 17, 2004

### BLaH!

I believe you made an error when calculating the final energy (and hence wavelength) of the X-ray. Do it like this. The final energy of the X-ray $$E_f = 0.99E_i$$ where the i stands for "initial". Now use the Einstein relation for the energy of a photon: $$E = \frac{hc}{\lambda}$$ to figure out the relationship between the final and initial wavelengths of the X-rays. You shouldn't get any type of quadratic term in $$\lambda$$

4. Oct 17, 2004

### Bobster

Thanks mate ! that was exactly my mistake.I cant believe I made that error but oh well !.

Cheers again !

This world needs more people like you

5. Oct 31, 2004

### Andrew Mason

I think the key is to get the recoil angle of the electron. It is almost 45 degrees ($tan\theta = .99$). Plug that into the Compton formula and you will get the magnitude of the wavelength change. That change represents a loss of one percent of the original energy.

AM